Daunomycin (British Patent 1003383, U.S. Pat. No. 3,616,242), adriamycin (U.S. Pat. No. 3,590,028, U.S. Pat. No. 3,803,124) and the like obtained from culture liquids of actinomycetes are known as anthracycline anticancer agents. They have broad anticancer spectrums against experimental tumors and also are clinically used widely as cancer chemotherapeutics. On the contrary, however, it is known that they frequently cause serious side effects, such as leukopenia, alopecia, myocardial disorder and the like.
In order to resolve this problem, various derivatives have been proposed. For example, pirarubicin (common name) aims at reducing its toxicity by introducing a tetrahydropyranyl group into the 4' position of the sugar moiety of adriamycin.
Also, epirubicin (common name) is a compound in which a hydroxyl group on the 4' position of the sugar moiety of adriamycin is bound to the a position, thereby attempting to reduce its toxicity.
However, though these drugs have lower toxicities in comparison with adriamycin, their problems such as limited total doses and the like are not completely settled yet.
On the other hand, it is a well known technique to make use of a high molecular micelle formed from a block copolymer to improve solubility of drugs which are slightly soluble in water. And it has been confirmed that high molecular block copolymer-drug complex pharmaceutical preparations obtained in Japanese Patent Application (Kokai) No. 2-300133, Japanese Patent Application (Kokai) No. 6-107565, Japanese Patent Application (Kokai) No. 5-955, Japanese Patent Application (Kokai) No. 5-124969, Japanese Patent Application (Kokai) No. 5-117385, Japanese Patent Application (Kokai) No. 6-206830, Japanese Patent Application (Kokai) No. 7-69900 and Japanese Patent Application (Kokai) No. 6-206815 are possessed of anticancer effects which are superior to those of adriamycin.